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Which of the following numbers are co-prime? (a) 18 and 35 (b) 15 and 37 (c) 30 and 415 (d) 17 and 168 (e) 216 and 215 (f) 81 and 16

Solution:

Coprime numbers are numbers that have only 1 as their HCF.

(a) 18 and 35
18 and 35 have no common factors, Therefore, 18 and 35 are coprime numbers.

(b) 15 and 37
As they have no common factors, 15 and 37 are co-prime numbers.

(c) 30 and 415
As they have a common factor 5, hence, 30 and 415 are not co-prime.

(d) 17 and 168
As they have no common factors, 17 and 168 are coprime numbers.

(e) 216 and 215
As they have no common factors, 216 and 215 are coprime numbers.

(f) 81 and 16
As they have no common factors, they are co-prime numbers.

Thus, the options a, b, d, e, f show the numbers that are co-prime.

Summary:

The options a, b, d, e, f have the numbers that are co-prime.